U.S. patent number 7,591,816 [Application Number 11/646,270] was granted by the patent office on 2009-09-22 for irrigated ablation catheter having a pressure sensor to detect tissue contact.
This patent grant is currently assigned to St. Jude Medical, Atrial Fibrillation Division, Inc.. Invention is credited to Hong Cao, Huisun Wang.
United States Patent |
7,591,816 |
Wang , et al. |
September 22, 2009 |
Irrigated ablation catheter having a pressure sensor to detect
tissue contact
Abstract
The invention relates to an irrigated ablation catheter that has
a pressure sensor to determine tissue contact as well as methods of
using the same. The irrigated ablation catheter contains fluid
tubing, an electrode with passages and a lumen and a pressure
sensor located inside the lumen of the electrode. In some
embodiments, a cooling fluid, such as saline, is passed through the
catheter.
Inventors: |
Wang; Huisun (Maple Grove,
MN), Cao; Hong (Savage, MN) |
Assignee: |
St. Jude Medical, Atrial
Fibrillation Division, Inc. (St. Paul, MN)
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Family
ID: |
39585039 |
Appl.
No.: |
11/646,270 |
Filed: |
December 28, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080161794 A1 |
Jul 3, 2008 |
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Current U.S.
Class: |
606/41 |
Current CPC
Class: |
A61B
18/1492 (20130101); A61B 2018/00029 (20130101); A61B
2218/002 (20130101); A61B 2090/065 (20160201) |
Current International
Class: |
A61B
18/14 (20060101) |
Field of
Search: |
;606/32-52
;600/403,404 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2005/048858 |
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Jun 2005 |
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WO |
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Other References
International Searching Authority; PCT/US07/88192; International
Search Report dated Jun. 13, 2008. cited by other .
International Searching Authority; PCT/US07/88192; Written Opinion
dated Jun. 13, 2008. cited by other .
Wittkampf, et al., "Radiofrequency Ablation With a Cooled Porous
Electrode Catheter," JACC vol. 11, No. 2, Feb. 1988: 17A Abstracts.
cited by other .
Wittkampf, et al., "Saline-Irrigated Radiofrequency Ablation
Electrode with External Cooling," Journal of Cardiovascular
Electrophysiology, vol. 16, No. 3, Mar. 2005. cited by
other.
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Primary Examiner: Peffley; Michael
Assistant Examiner: Hupczey, Jr.; Ronald J
Attorney, Agent or Firm: Dykema Gossett LLP
Claims
What is claimed:
1. An ablation catheter comprising: (a) an elongated tubing having
a distal end, a proximal end, and a lumen; (b) an electrode having
an inner cavity, a plurality of passages from the inner cavity to
an outer surface of the electrode, a distal end and a proximal end;
(c) a shaft having a distal end and a proximal end, said distal end
attached to the proximal end of electrode, the shaft being external
to the tubing; and (d) a pressure sensor mounted inside the inner
cavity of the electrode for sensing pressure change due to a change
in fluid flow exiting through at least one of the passages.
2. The ablation catheter of claim 1, wherein said electrode
comprises Pt, Ir, gold, a noble metal, or stainless steel.
3. The ablation catheter of claim 2, wherein said electrode
comprises a Pt and Ir alloy.
4. The ablation catheter of claim 1, wherein the pressure sensor is
a fiber optic pressure sensor.
5. The ablation catheter of claim 4, further comprising a fiber
optic cable connected to the fiber optic pressure sensor.
6. The ablation catheter of claim 1, wherein the total area of the
passages is smaller than the cross-sectional area of the lumen of
the tubing.
7. The ablation catheter of claim 1, wherein the shaft is
tubular.
8. The ablation catheter of claim 1, wherein the tubing comprises
radiopaque markers or radiopaque filler.
9. The ablation catheter of claim 1, wherein the electrode emits
radiofrequency energy.
10. An ablation catheter comprising: (a) an elongated tubing having
a distal end, a proximal end, and a lumen; (b) a manifold having a
distal end, a proximal end, a lumen, at least one passage from the
lumen to an outer surface of the manifold; (c) an electrode having
an inner cavity, at least one passage from the inner cavity to an
outer surface of the electrode, a distal end and a proximal end;
(d) a shaft having a distal end and a proximal end, said distal end
attached to the proximal end of the manifold and external to the
tubing; and (e) a pressure sensor mounted inside the inner cavity
of the electrode for sensing pressure change due to a change in
fluid flow exiting through the passage from the inner cavity to the
outer surface of the electrode, wherein said manifold is attached
to the proximal end of the tubing such that the lumen of the
manifold and the lumen of the tubing are connected, and wherein
said electrode is attached to the proximal end of the manifold such
that the lumen of the manifold is mated to the inner cavity of the
electrode.
11. The ablation catheter of claim 10, wherein said electrode
comprises Pt, Ir, gold, a noble metal, or stainless steel.
12. The ablation catheter of claim 11, wherein said electrode
comprises a Pt and Ir alloy.
13. The ablation catheter of claim 10, wherein the pressure sensor
is a fiber optic pressure sensor.
14. The ablation catheter of claim 13, further comprising a fiber
optic cable connected to the fiber optic pressure sensor.
15. The ablation catheter of claim 10, wherein the total area of
the passages is smaller than the cross-sectional area of the lumen
of the tubing.
16. The ablation catheter of claim 10, wherein the shaft is
tubular.
17. The ablation catheter of claim 10, wherein the tubing comprises
radiopaque markers or radiopaque filler.
18. The ablation catheter of claim 10, wherein the electrode emits
radiofrequency energy.
19. The ablation catheter of claim 10, the manifold comprises of a
thermally insulative material.
20. A method of ablation comprising: (a) providing an open
irrigated ablation catheter comprising an electrode having a lumen
and plurality of passages and a pressure sensor inside the lumen of
the electrode for sensing pressure change due to a change in fluid
flow exiting through at least one of the passages; (b) inserting
the catheter into a patient; (c) measuring the pressure in the
catheter inside the patient; (d) contacting a target tissue, (e)
determining if contacting of the target tissue has been made by (i)
measuring the pressure inside the catheter inside the patient after
tentative target tissue contact; and (ii) comparing this pressure
with that in step (c), wherein an increase in the pressure is
indicative of tissue contact due to change in fluid flow exiting
through at least one of the passages; and (f) ablating the target
tissue if there is contact.
21. The method of claim 20, wherein the electrode of the catheter
comprises Pt, Ir or alloy thereof.
22. The method of claim 20, wherein the pressure sensor of the
electrode is a fiber optic pressure sensor.
23. The method of claim 20, wherein the step of ablating comprises
supplying radiofrequency energy to the electrode.
24. The method of claim 20, wherein a cooling fluid is passed
through the catheter.
25. The method of claim 24, wherein the cooling fluid is
saline.
26. An ablation catheter comprising: (a) an elongated tubing having
a distal end, a proximal end, and a lumen; (b) a shaft having a
distal end, a proximal end, and a lumen, the shaft being external
to the elongated tubing; (c) a distal member coupled to the distal
end of the shaft to form an interior space of the catheter, the
distal member having at least one passage fluidicly coupled between
the interior space of the catheter and the outer surface of the
distal member, the interior space of the catheter being fluidicly
coupled to the lumen of the elongated tubing, the distal member
including an electrode; and (d) a pressure sensor disposed inside
the interior space of the catheter for sensing pressure change due
to a change in fluid flow exiting through the passage.
27. The ablation catheter of claim 26, wherein the electrode
includes at least one passage fluidicly coupled between the
interior space of the catheter and the outer surface of the distal
member.
28. The ablation catheter of claim 26, wherein the distal member
includes a manifold having a proximal end connected to the distal
end of the shaft and a distal end connected to the electrode.
29. The ablation catheter of claim 28, wherein the manifold
includes at least one passage fluidicly coupled between the
interior space of the catheter and the outer surface of the distal
member.
30. The ablation catheter of claim 28, wherein the manifold
comprises a thermally insulative material.
31. The ablation catheter of claim 28, wherein the electrode
includes at least one passage fluidicly coupled between the
interior space of the catheter and the outer surface of the distal
member, and wherein the manifold includes at least one passage
fluidicly coupled between the interior space of the catheter and
the outer surface of the distal member.
32. The ablation catheter of claim 26, wherein the distal member
includes an inner cavity forming a portion of the interior space of
the catheter, and wherein the pressure sensor is disposed inside
the inner cavity of the distal member.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. application Ser. No.
11/646,275, filed Dec. 28, 2006 and entitled Irrigated Ablation
Catheter System With Pulsatile Flow To Prevent Thrombus, now
pending; U.S. application Ser. No. 11/646,237, filed Dec. 28, 2006
and entitled Irrigated Ablation Catheter Having A Valve To Prevent
Backflow, now pending; and U.S. application Ser. No. 11/646,255,
filed Dec. 28, 2006 and entitled Cooled Ablation Catheter With
Reciprocating Flow, now pending. These applications are all hereby
incorporated by reference in their entirety as though fully set
forth herein.
BACKGROUND OF THE INVENTION
a. Field of the Invention
The instant invention relates to ablation catheters. In particular,
the instant invention relates to an irrigated ablation catheter
that has an internal pressure sensor to detect tissue contact and
methods of operating the catheter.
b. Background Art
Electrical stimulation of myocardial tissue controls the pumping
action of the heart. Stimulation of this tissue in various regions
of the heart is controlled by a series of conduction pathways
contained within the myocardial tissue. In a healthy heart,
contraction and relaxation of the heart muscle (myocardium) occur
in an organized fashion as electro-chemical signals pass
sequentially through the myocardium from the sinoatrial (SA) node,
which consist of a bundle of unique cells disposed in the wall of
the right atrium, to the atrioventricular (AV) node, and then into
the left and right ventricles via a route that includes the
His-Purkinje system. The AV node is located near the ostium of the
coronary sinus in the interatrial septum in the right atrium. Each
cell membrane of the SA node has a characteristic tendency of a
gradual leak of sodium ions over time leading to a periodic break
down of the cell membrane, thus allowing an inflow of sodium ions,
and thereby causing the SA node cells to depolarize. The SA node
cells are in communication with the surrounding atrial muscle cells
such that the depolarization of the SA node cells causes the
adjacent atrial muscle cells to also depolarize. This
depolarization results in atrial systole, during which the atria
contract to empty and fill blood into the ventricles. The AV node
detects the atrial depolarization from the SA node and, in turn,
relays the depolarization impulse into the ventricles via the
bundle of His and Purkinje fibers following a brief conduction
delay. The His-Purkinje system begins at the AV node and follows
along the membranous interatrial septum toward the tricuspid valve
through the AV septum and into the membranous interventricular
septum. At about the middle of the interventricular septum, the
His-Purkinje system splits into right and left branches, which
straddle the summit of the muscular part of the interventricular
septum.
Abnormal rhythms generally referred to as arrhythmia can occur in
the heart. Cardiac arrhythmias arise when the pattern of the
heartbeat is changed by abnormal impulse initiation or conduction
in the myocardial tissue. The term tachycardia is used to describe
an excessively rapid heartbeat resulting from repetitive
stimulation of the heart muscle. Such disturbances often arise from
additional conduction pathways that are present within the heart
either from a congenital developmental abnormality or an acquired
abnormality, which changes the structure of the cardiac tissue,
such as a myocardial infarction.
A common arrhythmia is Wolff-Parkinson-White syndrome (W-P-W). The
cause of W-P-W is generally believed to be the existence of an
anomalous conduction pathway or pathways that connect the atrial
muscle tissue directly to the ventricular muscle tissue, thus
bypassing the normal His-Purkinje system. These pathways are
usually located in the fibrous tissue that connects the atrium and
the ventricle.
Atrial arrhythmia may also occur. Three of the most common atrial
arrhythmia are ectopic atrial tachycardia, atrial fibrillation, and
atrial flutter. Atrial fibrillation can cause significant patient
discomfort and even death because of a number of associated
problems, including e.g., an irregular heart rate (which causes
patient discomfort and anxiety), loss of synchronous
atrioventricular contractions (which compromises cardiac
hemodynamics, resulting in varying levels of congestive heart
failure) and stasis of blood flow (which increases the likelihood
of thromboembolism).
In the past, problems associated with arrhythmia have been treated
with pharmacological treatment. Such treatment may not be effective
in all patients and is frequently plagued with side effects,
including, e.g., dizziness, nausea, vision problems, and other
difficulties.
Alternatively, such disturbances are treated by identifying the
conductive pathways and then severing part of this pathway by
destroying these cells, which make up a portion of the pathway.
Traditionally, this has been done by either cutting the pathway
surgically; freezing the tissue, thus destroying the cellular
membranes; or by heating the cells, thus denaturing the cellular
proteins. The resulting destruction of the cells eliminates their
electrical conductivity, thus destroying, or ablating, a certain
portion of the pathway. By eliminating a portion of the pathway,
the pathway may no longer maintain the ability to conduct, and the
tachycardia ceases.
Catheters are a common medical tool that has been used for many
years. They are employed, e.g., for medical procedures to examine,
diagnose, and treat while positioned at a specific location within
the body that is otherwise inaccessible without more invasive
procedures. In such procedures, a catheter is first inserted into a
vessel near the surface of the body and the guided to a specific
location within the body. For example, a catheter may be used to
convey an electrical stimulus to a selected location within the
human body or a catheter with sensing electrodes may be used to
monitor various forms of electrical activity in the human body.
Catheters have increasingly become a common medical procedure for
the treatment of certain types of cardiac arrhythmia. Catheter
ablation is based on the idea that by ablation (i.e., destroying)
abnormal tissue areas in the heart, its electrical system can be
repaired and the heart will return to a normal rhythm. During
catheter ablation, the catheter is typically inserted in an artery
or vein in the leg, neck, or arm of the patient and then threaded,
sometimes with the aid of a guide wire or introducer, through the
vessels until a distal tip of the catheter reaches the desired
location for the medical procedure in the heart.
Most often, cardiac ablation is used to treat supraventricular
tachycardias, or SVTs. Types of SVTs are atrial fibrillation,
atrial flutter, AV nodal reentrant tachycardia, AV reentrant
tachycardia, and atrial tachycardia. Less frequently, ablation can
treat heart rhythm disorders that begin in the heart's lower
chambers, known as the ventricles. The most common, ventricular
tachycardia may also be the most dangerous type of arrhythmia
because it can cause sudden cardiac death. For patients at risk for
sudden cardiac death, ablation often is used along with an
implantable cardioverter device (ICD). The ablation decreases the
frequency of abnormal heart rhythms in the ventricles and therefore
reduces the number of ICD shocks a patient may experience. For many
types of arrhythmias, catheter ablation is successful in 90-98
percent of cases, thus eliminating the need for open-heart
surgeries or long-term drug therapies.
During conventional catheter ablation procedures, an energy source
is in contact with cardiac tissue to heat the tissue and create a
permanent scar or lesion that is electrically inactive or
non-contractile. These lesions are designed to interrupt existing
conduction pathways commonly associated with arrhythmias within the
heart. The particular area for ablation depends on the type of
underlying arrhythmia. One common ablation procedure treats
atrioventricular nodal reentrant tachycardia (AVNRT). The use of
electrode catheters for ablating specific locations within the
heart has also been disclosed in, e.g., U.S. Pat. Nos. 4,641,649,
5,228,442, 5,231,995, 5,263,493, and 5,281,217.
Many variations of ablations procedures are known. For example,
ablation of fast or slow AV nodal pathways is disclosed in Singer
et al., Catheter Ablation for Arrhythmias, Clinical Manual of
Electrophysiology, 421-431 (1993).
Another medical procedure using ablation catheters with sheaths to
ablate accessory pathways associated with W-P-W using both a
transseptal and retrograde approach is discussed in Saul et al.,
Catheter Ablation of Accessory Atrioventricular Pathways in Young
Patients: Use of long vascular sheaths, the transseptal approach
and a retrograde left posterior parallel approach, Journal of the
American College of Cardiology, 21, 571-583 (1993). Additional
catheter ablation procedures are disclosed in Swartz,
Radiofrequency Endocardial Catheter Ablation of Accessory
Atrioventricular Pathway Atrial Insertion Sites, Circulation, 87,
487-499 (1993).
Ablation of a specific target requires precise placement of the
ablation catheter within the heart. Precise positioning of the
ablation catheter is especially difficult due the physiology of the
heart, particularly since the heart continues to beat throughout
the ablation procedures. Typically, the choice of placement of the
catheter is determined by a combination of electrophysiological
guidance and fluoroscopy. Fluoroscopy is placement of the catheter
in relation to known features of the heart, which are marked by
radiopaque diagnostic catheters that are placed in or at known
anatomical structures, such as the coronary sinus, high right
atrium, and the right ventricle.
Ablation procedures using guiding introducers to direct an ablation
catheter to a particular location in the heart for treatment of
atrial arrhythmia have been disclosed in, e.g., U.S. Pat. Nos.
5,427,119, 5,497,774, 5,564,440, 5,575,766, 5,628,316, and
5,640,955. During these procedures, ablation lesions are produced
in the heart.
A variety of energy sources can be used to supply the energy
necessary to ablate cardiac tissue and create a permanent lesion.
Such energy sources include direct current, laser, microwave, and
ultrasound. Because of problems associated with the use of DC
current, radiofrequency (RF) has become the preferred source of
energy for ablation procedures. The use of RF energy for ablation
has been disclosed, e.g., in U.S. Pat. Nos. 4,945,912, 5,242,441,
5,246,438, 5,281,213, 5,281,218, and 5,293,868. The use of RF
energy with an ablation catheter contained within a transseptal
sheath for the treatment of W-P-W in the left atrium is disclosed
in Swartz et al., Radiofrequency Endocardial Catheter Ablation of
Accessory Atrioventricular Pathway Atrial Insertion Sites,
Circulation, 87: 487-499 (1993). See also Tracey, Radio Frequency
Catheter Ablation of Ectopic Atrial Tachycardia Using Paced
Activation Sequence Mapping, J. Am. Coll. Cardiol. 21: 910-917
(1993).
In addition to radiofrequency ablation catheters, thermal ablation
catheters are also used. During thermal ablation, a heating
element, secured to the distal end of a catheter, heats thermally
conductive fluid. This fluid then contacts the human tissue to
raise its temperature for a sufficient period of time to ablate the
tissue. A method and device for thermal ablation using heat
transfer is disclosed in U.S. Pat. No. 5,433,708. U.S. Pat. No.
5,505,730 discloses another thermal ablation procedure. This
procedure utilizes a thermal electrode secured to a catheter and
located within a balloon with openings in that balloon. The
openings permit a heated conductive fluid introduced into the
balloon from the catheter to escape to contact the tissue to be
ablated.
Conventional ablation procedures use a single electrode secured to
the tip of an ablation catheter. It has become increasingly more
common to use multiple electrodes affixed to the catheter body.
Such ablation catheters often contain a distal tip electrode and a
plurality of ring electrodes as disclosed in, e.g., U.S. Pat. Nos.
4,892,102, 5,228,442, 5,327,905, 5,354,297, 5,487,385, and
5,582,609.
During conventional ablation procedures, the ablating energy is
delivered directly to the cardiac tissue by an electrode on the
catheter placed against the surface of the tissue to raise the
temperature of the tissue to be ablated. The increase in tissue
temperature also results in a rise in the temperature of blood
surrounding the electrode. This rise in temperature often results
in the formation of coagulum on the electrode, which in turn
reduces the efficiency of the ablation electrode. Thus, to achieve
efficient and effective ablation, coagulation of blood should be
avoided. This coagulation problem can be especially significant
when linear ablation lesions or tracks are produced because such
linear ablation procedures take more time than ablation at only a
single location.
The formation of linear lesions within a heart via conventional
ablation tip electrode requires use of procedures such as e.g., a
"drag burn." A "linear lesion" means an elongate, continuous
lesion, which may be straight or curved, that blocks electrical
conduction. During a "drag burn" procedure, while energy is
supplied to the electrode, the electrode is drawn across the tissue
to be ablated, producing a line of ablation. Alternatively, a
series of points of ablation are formed in a line created by moving
the tip electrode incremental distances across the cardiac tissue.
The effectiveness of these procedures depends on a number of
variables such as e.g., (i) the position and contact pressure of
the tip electrode of the ablation catheter against the cardiac
tissue, (ii) the time that the tip electrode of the ablation
catheter is placed against the tissue, (iii) the amount of coagulum
formed as a result of heat generated during the ablation procedure,
and (iv) other variables associated with a beating heart,
especially an erratically beating heart. An uninterrupted track of
cardiac tissue needs to be ablated as unablated tissue or
incompletely ablated tissue may remain electrically active, thereby
permitting the continuation of stray circuits that cause
arrhythmia.
More efficient ablation can be achieved if a linear lesion of
cardiac tissue is formed during a single ablation procedure. The
production of linear lesions in the heart by use of an ablation
catheter is disclosed in, e.g., U.S. Pat. Nos. 5,487,385,
5,582,609, and 5,676,662. A specific series of linear lesions
formed in the atria for the treatment of atrial arrhythmia are
disclosed in U.S. Pat. No. 5,575,766.
Physical contact of the cardiac tissue with an electrode of the
ablation catheter is typically used to perform these procedures on
electrically inactive or non-contractile tissue. Conventional tip
electrodes with adjacent ring electrodes cannot perform this type
of procedure, however, due to the high amount of energy necessary
to ablate sufficient tissue to produce a complete linear lesion. In
addition, conventional ring electrode ablation may leave holes or
gaps in a lesion, which can provide a doorway for the creation of
unwanted circuits.
U.S. Pat. No. 5,334,193 discloses an ablation catheter for use in
the heart that contains a pair of intertwined helical electrodes.
The helically wound electrode is affixed to the surface of the
catheter body over a distance of about eight centimeters from the
distal tip of the catheter body. Other helical electrodes are
disclosed in WO 95/10319 as well as U.S. Pat. Nos. 4,161,952,
4,776,334, 4,860,769, 4,934,049, 5,047,026, and 5,542,928.
As discussed a variety of energy such as radiofrequency (RF),
microwave, ultrasound, and laser energy have been used for
ablation. With RF energy, a catheter with a conductive inner core
and a metallic tip are placed in contact with the myocardium and a
circuit is completed with a patch placed on the patient's body
behind the heart. The catheter is coupled to a RF generator such
that application of electrical energy creates localized heating in
the tissue adjacent to the distal (emitting) electrode. The peak
tissue temperatures during catheter delivered application of RF
energy to the myocardium occur close to the endocardial surface,
such that the lesion size produced is limited by the thermodynamics
of radiant heat spread from the tip. The amount of heating which
occurs is dependent on the area of contact between the electrode,
and the tissue and the impedance between the electrode and the
tissue. The higher the impedance, the lower the amount of energy
transferred into the tissue.
During RF catheter ablation, local temperature elevation can result
in coagulum formation on the ablation electrode, resulting in
impedance rise. As the impedance increases, more energy is passed
through the portion of the tip without coagulation, creating even
higher local temperatures and further increasing coagulum formation
and the impedance. Finally, enough blood coagulates onto the tip
that no energy passes into the tissue. The catheter must now be
removed from the vascular system, the tip area cleaned and the
catheter repositioned within the heart at the desired location. Not
only can this process be time consuming, but also it may be
difficult to return to the previous location because of the reduced
electrical activity in the regions, which have previously been
ablated. A recent study has also demonstrated the formation of a
so-called soft thrombus during experimental ablations (Demonlin et
al. Soft thrombus formation in radiofrequency catheter ablation,
Pacing clin. electrophysiol. 25: 1219-1222 (2002)). The formation
of the so-called soft thrombus results from heat induced protein
denaturation and aggregation and occurs independent of heparin
concentration in serum.
To prevent the occurrence of, e.g., soft thrombus, blood
coagulation, and steam pop during ablation, the catheter may be
cooled by passing a fluid through the catheter during ablation.
Saline irrigation is an effective way to cool the ablation
electrode and keep efficient flow around the electrode to prevent
blood coagulation. Furthermore, the surface cooling that results
from the saline irrigation reduces heating at the point of highest
current density where excessive temperatures would normally produce
charring, crater formation and impedance rises (Thomas et al., A
comparison of open irrigated and non-irrigated tip catheter
ablation for pulmonary vein isolation, Europace 6: 330-335 (2004)).
Open irrigated ablation catheters are currently the most common
irrigated catheters in the electrophysiology field. Examples of
these devices include Thermocool.RTM. by Biosense Webster and
Coolpath.RTM. by Irvine Biomedical.
It is also important to ensure that the appropriate amount of
energy necessary to destroy the tissue is delivered. In an RF
ablation catheter, this is achieved by maintaining a good contact
between the target tissue and electrode. A number to technologies
have been developed to detect the contact between the target tissue
and electrode. Most of these methods rely on deflection of the
catheter to detect catheter contacting.
There remains a need to detect contact between the catheter and
target tissue without bending of the catheter.
BRIEF SUMMARY OF THE INVENTION
It is desirable to be able to provide an irrigated ablation
catheter that detects contacting between the target tissue and
catheter without relying on catheter deflection.
One embodiment of the invention is an irrigated ablation catheter
with a pressure sensor mounted in the catheter. The irrigated
ablation catheter may utilize radiofrequency energy to ablate the
target tissue. The irrigated ablation catheter may also be packaged
as part of a kit.
The irrigated ablation catheter includes an elongated tubing having
a distal end, a proximal end, and a lumen. The irrigated ablation
catheter also has an electrode attached to the distal end of the
tubing. The electrode has an inner cavity, a plurality of passages
from the inner cavity to an outer surface of the electrode as well
as a distal end and a proximal end. The catheter also has a shaft
with a distal end and a proximal end. The distal end of the shaft
is attached to the proximal end of electrode and external to the
tubing. The catheter also includes a pressure sensor located inside
the inner cavity of the electrode.
The electrode may be made of platinum (Pt), iridium (Ir), gold, a
gold alloy, a noble metal, or stainless steel. In one embodiment,
the electrode is made from a Pt and Ir alloy. The pressure sensor
may be a fiber optic sensor, which may be connected to a fiber
optic cable. The tubing is flexible. The total area of the passages
in the electrode may be smaller than the cross-sectional area of
the lumen of the tubing. The shaft may be tubular and the tubing
may contain radiopaque markers or radiopaque filler. A cooling
fluid, such as, e.g., saline, may be passed through the
catheter.
Another embodiment of the invention is an irrigated ablation
catheter encompassing an elongated tubing connected to a manifold,
which in turn is connected to an electrode, a shaft connected to
the manifold and a pressure sensor. The irrigated ablation catheter
may use RF energy.
The elongated tubing has a distal end, a proximal end, and a lumen.
The manifold has a distal end, a proximal end and a lumen, and at
least one passage from the lumen to an outer surface of the
manifold. The manifold is attached to the proximal end of the
flexible tubing such that the lumen of the manifold and the lumen
of the tubing are connected. The electrode has an inner cavity, at
least one passage from the inner cavity to an outer surface of the
electrode, a distal end, and a proximal end. The electrode attached
to the proximal end of the manifold such that the lumen of the
manifold is mated to the inner cavity of the electrode. The shaft
has a distal end and a proximal end. The distal end of the shaft is
attached to the proximal end of the manifold and external to the
flexible tubing. The shaft may be tubular. The pressure sensor is
located inside the inner cavity of the electrode.
The electrode may contain Pt, Ir, gold, a gold alloy, a noble
metal, stainless steel or a Pt and Ir alloy. The pressure sensor
may be a fiber optic pressure sensor, which may be connected to a
fiber optic cable. In one embodiment, the total area of the
passages is smaller than the cross-sectional area of the lumen of
the flexible tubing. The tubing may contain radiopaque markers or
radiopaque filler. A cooling fluid, such as e.g., saline, may be
passed through the catheter.
The invention also encompasses methods of using irrigated ablation
catheters. In one embodiment, the method of ablation has the steps
of:
(a) providing an open irrigated ablation catheter comprising an
electrode having a lumen and plurality of passages ways and a
pressure sensor inside the lumen of the electrode;
(b) inserting the catheter into a patient;
(c) measuring the pressure in the catheter inside the patient;
(d) contacting a target tissue,
(e) determining if contacting of the target tissue has been made by
(i) measuring the pressure inside the catheter inside the patient
after tentative target tissue contact; and (ii) comparing this
pressure with that in step (c), wherein an increase in the pressure
is indicative of tissue contacting; and
(f) ablating the target tissue.
This method may be used when the catheter has a manifold that is
mounted to the electrode, when the electrode of the catheter is Pt,
Ir, or alloy thereof, when the pressure sensor of the electrode is
a fiber optic pressure sensor and when a cooling fluid, such as
e.g., saline, is passed through the catheter. The step of ablating
may employ radiofrequency energy.
Another embodiment of the invention is an ablation catheter that
has (a) elongated tubing having a distal end, a proximal end, and a
lumen, (b) a shaft having a distal end, a proximal end, and a
lumen, the shaft being external to the elongated tubing; (c) a
distal member coupled to the distal end of the shaft to form an
interior space of the catheter, the distal member having at least
one passage fluidicly coupled between the interior space of the
catheter and the outer surface of the distal member, the interior
space of the catheter being fluidicly coupled to the lumen of the
elongated tubing, the distal member including an electrode, and (d)
a pressure sensor disposed inside the interior space of the
catheter.
In such a catheter, the electrode may include at least one passage
fluidicly coupled between the interior space of the catheter and
the outer surface of the distal member. Furthermore, the distal
member may include a manifold having a proximal end connected to
the distal end of the shaft and a distal end connected to the
electrode. This manifold may have at least one passage fluidicly
coupled between the interior space of the catheter and the outer
surface of the distal member. Additionally, the manifold may be
made of a thermally insulative material. In one embodiment of such
an ablation catheter, the electrode includes at least one passage
fluidicly coupled between the interior space of the catheter and
the outer surface of the distal member, and the manifold includes
at least one passage fluidicly coupled between the interior space
of the catheter and the outer surface of the distal member. The
distal member may include an inner cavity forming a portion of the
interior space of the catheter, and the pressure sensor may be
disposed inside the inner cavity of the distal member.
The foregoing and other aspects, features, details, utilities, and
advantages of the present invention will be apparent from reading
the following description and claims, and from reviewing the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
FIG. 1 is a cross-sectional view of one embodiment of an irrigated
ablation catheter according to the instant disclosure. FIG. 1 shows
the cross-section of the electrode at the distal end of an ablation
catheter with a pressure sensor located inside the lumen of the
electrode.
FIG. 2 is a cross-sectional view of another embodiment of an
irrigated ablation catheter according to the instant disclosure.
FIG. 2 shows the cross-section of the electrode and manifold at the
distal end of an ablation catheter with a pressure sensor located
inside the lumen of the electrode.
FIG. 3 is a side view of the flow and pressure change inside the
distal end of an irrigated catheter according to one embodiment of
the invention at a perpendicular position as a result of tissue
contacting. FIG. 3A shows the flow when there is no contacting with
the target tissue. FIG. 3B shows the flow when there is
contacting.
FIG. 4 is an axial view at horizontal orientation of the flow and
pressure change inside distal the irrigated catheter according to
one embodiment of the invention because of tissue contacting. FIG.
4A shows the flow when there is no contacting with the target
tissue. FIG. 4B shows the flow when there is contacting.
FIG. 5 is a side view at horizontal orientation of the flow and
pressure change inside the distal end of an irrigated catheter
according to one embodiment of the invention as a result of tissue
contacting. FIG. 5A show the flows when there is no contacting with
the target tissue. FIG. 5B shows the flow when there is
contacting.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the certain embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings. FIGS. 1 and 2 show different embodiments of
an irrigated ablation catheter according to the instant disclosure.
As described below, the FIGS. 3 to 5 illustrate the flow and
pressure change inside an irrigated ablation catheter according to
the instant disclosure.
As used herein, "proximal" refers to the direction away from the
body of a patient and towards a clinician. Furthermore, as used
herein "distal" refers to the direction toward the body of a
patient and away from the clinician.
One embodiment of the invention is an irrigated ablation catheter
that utilizes an electrode with a plurality of passageways and a
pressure sensor inside the electrode. Referring to FIG. 1, side
elevational view of catheter 100 is shown. Catheter 100 has
elongated flexible tubing 110, pressure sensor 106, shaft 108, and
electrode 102. The elongated flexible tubing 110 has a distal end,
a proximal end, and a lumen 112. The electrode 102 has an inner
cavity 114, a plurality of passages 104 from the inner cavity to an
outer surface of the electrode, as well as a distal end and a
proximal end. The electrode 102 is attached to flexible tubing 110
such that the inner cavity 114 of electrode 102 is connected to the
lumen 112 of the flexible tubing 110. Pressure sensor 106 is
located inside the inner cavity 114.
Catheter 100 may be of varying lengths, the length being determined
by the application for the catheter.
Electrode 102 may be made of any electro-conductive material
suitable for medical use. Electrode 102 may be a single electrode
or multiple electrodes. The electrode may contain gold, a gold
alloy, a noble metal, stainless steel, platinum, and/or iridium.
The electrode may contain a platinum-iridium alloy. In one
embodiment of the invention, the electrode is made from a
platinum-iridium alloy. The length of the electrode may be at least
4 mm alternatively from about 1 cm to about 6 cm. In another
embodiment of the invention, the electrode comprises an
electro-conductive coating.
The plurality of passages 104 from the inner cavity 114 to the
outside allows free movement of fluid from the inside to the
outside of the cavity. The plurality of passages 104 are positioned
on the electrode 102 in areas where the electrode may contact the
target tissue. In one embodiment of the invention, the electrode
has five to seven passages. In another embodiment, the electrode
has less than five passages. In yet another embodiment, the
electrode has up 15 passages. The diameter of the passages may
range from about 0.010 in. to about 0.020 in. (about 0.25 mm to
about 0.5 mm). In some embodiments, the plurality of passages 104
is smaller in size than blood cells. In one embodiment of the
invention, the total area of the passages is smaller than the
cross-sectional area of the lumen of the flexible tubing.
The pressure sensor 106 may be suspended in the inner cavity 114.
Alternatively, the pressure sensor may be mounted inside the inner
cavity 114. The pressure sensor 106 measures the pressure of fluid
inside the electrode 102. The size of the pressure sensor needs to
be minimized so as not to impede fluid flow inside the catheter.
This pressure measurement is relayed to the outside. In one
embodiment of the invention, this pressure measurement is relayed
to the outside via a relay cable. In another embodiment of the
invention, this pressure measurement is relayed to the outside
wirelessly. In another embodiment of the invention, the pressure
measurement may be relayed to a computational device (such as e.g.,
a personal computer) that also controls the flow of energy into
electrode 102.
Shaft 108 may be a tubular shaft and may be made of a corrosion
resistant material such as e.g., stainless steel. In some
embodiments, shaft 108 is made of a rigid material. Shaft 108 has a
distal end and a proximal end. The distal end of shaft 108 is
attached to the proximal end of electrode 102 and external to the
flexible tubing 110.
Flexible tubing 110 may be of varying length, the length being
determined by the application for catheter 100. Flexible tubing 110
is hollow on the inside, thereby creating a lumen 112. In some
embodiments, this lumen should have a diameter of at least 0.2 mm,
including from about 0.3 to about 1.0 mm.
The flexible tubing may be made from materials suitable for medical
use. The flexible tubing may be a flexible durable material (such
as e.g., polyethylene), including thermoplastics (such as e.g.,
nylon) in which braiding is embedded. The flexible tubing may be
constructed from a number of different polymers. Exemplary polymers
include e.g., polypropylene, oriented polypropylene, polyethylene,
crystallized polyethylene terephthalate, polyethylene
terephthalate, polyester, and polyvinyl chloride. Alternatively,
the flexible tubing may be made from conventional flexible
conductively coatable materials, such as e.g., polyurethanes,
polyether-block amides, polyolefins, silicone, nylons,
polytetrafluoroethylene, polyvinylidene fluoride, fluorinated
ethylene propylene polymers, and other conventional materials. The
tubing may include radiopaque markers or radiopaque filler such as
bismuth or barium sulfate.
In one embodiment of the invention, the flexible tubing is made up
from a series of different materials to allow for different
material stiffness different sections of the catheter. These
sections of different material enable the flexible tubing (and
therefore the catheter) to have different mechanical properties
such as e.g., flexibility, at different locations along the tubing.
Suitable materials to create these different sections include
Pebax.RTM. resin (AUTOFINA Chemicals, Inc., Philadelphia, Pa.) and
other polyether-block co-polyamide polymers.
In one embodiment of the invention, the flexible tubing is used to
deliver a cooling fluid such as e.g., saline. This cooling fluid is
delivered to the ablation site in order to cool the tip of the
catheter so that a larger amount of heart tissue can be destroyed.
The rate of flow of the cooling fluid can be varied. The flow rate
may range from about 10 mL/min to about 30 mL/min. In one
embodiment of the invention, the flow rate may range from about 13
mL/min to about 17 mL/min. In another embodiment, the rate of flow
of the cooling fluid is constant (i.e., the cooling fluid is moving
at a fixed flow rate).
Another embodiment of the invention is an irrigated ablation
catheter that utilizes an electrode, a manifold, and a pressure
sensor. Referring to FIG. 2, a side elevational view of catheter
200 is shown. Catheter 200 has flexible tubing 210, electrode 202,
manifold 206, pressure sensor 204, and shaft 208. Flexible tubing
210 has a proximal, a distal end, and lumen 212. Manifold 206 is
connected to the distal end of flexible tubing 210. Manifold 206
has a lumen 214 inside of which pressure sensor 204 is located
(i.e., suspended or mounted). Manifold 206 is connected to
electrode 202. Shaft 208 is also connected to manifold 206 external
to the flexible tubing. Electrode 202 and manifold 206 have a
plurality of passages 216, which connect the inner cavity 218 of
electrode 202 and the lumen 214 of manifold 206 to the outside.
Fluid tube 210 may be of varying lengths, the length being
determined by the application for the catheter 200. Fluid tube 210
can be made of a flexible durable material, including
thermoplastics such as nylon, in which a braiding is embedded. The
electrode 202 may be a single electrode or multiple electrodes
surrounding the distal surface of catheter 200. The electrode 200
may have a length of at least 4 mm alternatively from about 1 cm to
about 6 cm. Shaft 208 may be made of a rigid material.
The manifold 206 separates the electrode 202 from the fluid tube
210 of catheter 200. Thus, the manifold 202 insulates the electrode
202 from the remainder of the catheter 200. It also minimizes
contact between saline inside the catheter and the electrode. The
distal passage 220 oriented along the axis at the tip of the
electrode 202 includes an insulative lining 222. The insulative
lining 222 insulates the distal passage 220 from the electrode 202.
The manifold 206 may be made of a variety of materials that have
insulating properties. The manifold may be made from a plastic such
as e.g., acetal, polyetheretherketone (PEEK), and high-density
polyethylene (HDPE).
In one embodiment of the invention, the electrode 202 does not have
an inner cavity. In that embodiment, the plurality of passages 216
directly connects the lumen 214 of manifold 206 to the outside. In
another embodiment of the invention, the electrode 202 does not
have distal passage 220. In that alternate embodiment, only the
manifold 206 has passages 216.
Catheter 200 has a plurality of passages in the manifold and
electrode. In one embodiment, there may be five to seven passages.
In another embodiment, the manifold and electrode combined have
less than five passages. In yet another embodiment, the manifold
and electrode have up to 15 passages.
The pressure sensor 106 and pressure senor 204 may be a fiber optic
pressure sensor, which relays pressure measurements to the outside
via use of a fiber optic cable. Such a fiber optic pressure sensor
may be as small as 0.5 mm in width and only a few nanometers long.
The fiber optic cable may be as small as 0.17 mm in diameter. The
fiber optic pressure sensor may be one of the commercially
available sensors such as the FOBPS family of fiber optic pressure
sensors by World Precision Instruments. This pressure sensor may be
operably linked to the electrode.
An open irrigation catheter according to the instant disclosure can
be operated with a fixed flow rate of cooling fluid inside the
catheter (a so-called fixed flow condition). Thus, when an open
irrigated ablation catheter has contact with tissue, some of the
plurality of openings on the distal electrode will be plugged by
the tissue. The pressure inside the electrode will increase as a
function of the reduced open irrigation area as well as the fixed
flow condition.
FIG. 3 illustrates the flow and pressure change inside the distal
end of an irrigated ablation catheter according to one embodiment
of the invention. FIG. 3 is a side view of the tip of a catheter at
perpendicular orientation. Referring to FIG. 3, only the tip of the
catheter 300 is visible. The tip of the catheter has electrode 302
mated to hollow flexible tubing 304. The electrode has a lumen 306
and plurality of passages 308. The plurality of passages 308
connect with the lumen 306 such that fluid can flow into and out of
the lumen. Pressure sensor 310 is suspended inside lumen 306. Since
the pressure sensor 310 is suspended inside the lumen 306, it
measures the pressure inside container created by fluid moving in
and out of the container. FIG. 3A shows the fluid and pressure flow
in the catheter when there is no contacting with a target tissue,
while FIG. 3B shows the fluid and pressure flow in the catheter
when there is contacting. In the absence of any contacting (as seen
in FIG. 3A), there is a fixed flow of fluid from the inside of the
catheter tip to the outside and therefore a constant pressure. When
the catheter 300 contacts target tissue 312, one or more of
plurality of passages 308 are blocked by the tissue. Thus, the
pressure inside the catheter will increase. This increase in
pressure is then detected by the pressure sensor. Based on this
increase in pressure, an operator of the catheter will then
recognize that tissue contact has been made and ablation can
proceed. Alternatively, the increase in pressure is operatively
linked to the electrode. Thus, upon an increase in pressure, the
electrode will be triggered automatically.
FIG. 4 illustrates the flow and pressure change inside the distal
end of an irrigated ablation catheter according to one embodiment
of the invention based on an axial view of the catheter at
horizontal or parallel orientation. In FIG. 4 only electrode 402,
plurality of passages 404, lumen 406, and pressure sensor 408 of
catheter 400 are visible. The plurality of passages connects the
lumen 406 to the outside. When the catheter 400 is not in contact
with a tissue (as seen in FIG. 4A), fluid flows from the catheter
to the outside at a fixed rate thereby maintaining a constant
pressure inside the catheter. When catheter 400 is in contact with
target tissue 410 (as seen in FIG. 4B), a number of the plurality
of passages 404 become blocked as a result of which the pressure
increases inside the catheter. Again, based on this increase in
pressure, an operator of the catheter will then recognize that
tissue contact has been made and ablation can proceed.
Alternatively, the increase in pressure is operatively linked to
the electrode so that the electrode is triggered automatically upon
an increase in pressure.
FIG. 5 illustrates the flow and pressure change inside the distal
end of an irrigated ablation catheter according to one embodiment
of the invention based on a side view of the catheter at horizontal
or parallel orientation. Only the tip of catheter 500 is shown.
Catheter 500 has electrode 502 connected to hollow flexible tubing
504. The electrode 502 has a plurality of openings 506, which
connect the lumen 508 with the outside. Inside lumen 508, pressure
sensor 510 is suspended. In the non-contacting state (as shown in
FIG. 5 A), fluid moves out of the electrode through plurality of
openings 506. This flow of fluid is at a constant rate and
therefore the pressure inside the catheter is constant. In the
contacting state (as shown in FIG. 5 B), one or more of the
plurality of openings 506 are blocked due to contact of the
electrode 502 with target tissue 512. Because of the contacting,
the pressure inside the catheter will increase. This increase in
pressure is detected by the pressure sensor and indicates to the
operator of the catheter that tissue contact has been made.
While only the distal end (i.e., the tip) of an irrigated catheter
is shown in FIGS. 1 and 2, one of skill in the art would understand
that a complete catheter set-up has additional elements well known
to those of skill in the art. For example, a complete catheter
set-up may contain a catheter (with flexible tubing and an
electrode), a pressure sensor, an energy source (such as e.g., an
RF generator), a pump that supplies the cooling fluid and a
proximal end control handle. The length of the catheter may be from
about 50 cm to about 150 cm. The diameter of the catheter is within
ranges well known in the industry, including, from about 4 to 16
French.
In some embodiments, the source for energy emitted by the electrode
of an irrigated ablation catheter according to the instant
disclosure is radiofrequency energy, although other sources for
energy can be utilized including direct current, laser, ultrasound,
and microwave. During the ablation procedure, the radiofrequency
energy from the electrode is conducted to the tissue to be ablated.
If sufficient energy is conducted to the tissue for a sufficient
period of time, a satisfactory ablation lesion is formed. The
lesion being formed should have an adequate depth along the entire
length of the lesion to avoid gaps.
The energy source may be an RF generator. In one embodiment of the
invention, the RF generator may provide up to 150 watts of power at
about 500 kHz, and will have capability for both temperature
monitoring and impedance monitoring. A suitable generator would be,
for example, a Model No. EPT-1000 available from the EP
Technologies Division of Boston Scientific Corp. of Natick, Mass.
In another embodiment of the invention, the RF generator may
provide up to 70 W at 550-kHz of unmodulated sine wave output.
Temperature sensors, such as e.g., thermistors or thermocouples,
may be secured to the surface of the catheter to monitor the
temperature of the tissue being ablated. Thus, these thermosensing
devices determine whether sufficient energy has been applied to the
tissue to create an adequate linear lesion. After the ablation
procedure is completed, a sensing electrode, such as a tip
electrode, may be utilized as a sensing system to determine if the
arrhythmia has been eliminated at the particular location within
the heart. Additional ablation lesions or tracks can then be
produced using the ablation catheter at the same or different
locations within the heart.
In one embodiment of the invention, the catheter has multiple
individually controllable electrodes on the tip of the catheter
that contacts the tissue. Such individually controllable electrodes
allow ablation to proceed only in areas where the electrode has
made contact with the tissue. This minimizes the amount of heat
created at the tip of the electrode and therefore minimizes the
amount of coagulum.
In operation, a modified Seldinger technique is normally used for
the insertion of the associated dilators, introducers, and ablation
catheter into the body. The appropriate vessel is accessed by
needle puncture. The soft flexible tip of an appropriately sized
guidewire is then inserted through, and a short distance beyond,
the needle into the vessel. Firmly holding the guidewire in place,
the needle is removed. The guidewire is then advanced through the
vessel into the appropriate portion of the heart for the ablation
procedure. A preformed, shaped guiding introducer or guiding
introducer system, such as those disclosed in U.S. Pat. No.
5,575,766, may be utilized to assist in proper placement of the
ablation catheter in the heart. Alternatively, or additionally, the
ablation catheter may contain a mechanism to make it steerable,
such as a pull wire, so that the ablation catheter may be guided
within the vessel or chamber of the human body to be ablated
without use of a guiding introducer. The ablation catheter can also
be directed to the location to be ablated by other steering
mechanism, such as a rail or a guidewire. In the heart, tissue
contact is verified based on pressure measurements.
In one embodiment, with a guidewire in place, the dilator is placed
over the guidewire with the appropriate guiding introducer, or
guiding introducer system. The dilator and the guiding introducer
or guiding introducer system generally forms an assembly to be
advanced together along the guidewire into the appropriate vessel.
After insertion of the assembly, the guidewire is then
withdrawn.
The guiding introducer or guiding introducer system for use in the
heart is then passed over the guidewire through its lumen and
positioned to allow ablation and mapping procedures to be performed
at the appropriate location in the heart. Once the guiding
introducer or guiding introducer system is in place at the
appropriate location within the heart, the ablation catheter is
advanced through the lumen of the guiding introducer or guiding
introducer system.
After the desired location for ablation is determined, and the
ablation catheter has been guided to that location, the electrode
of the catheter is at or near the tissue to be ablated. Placement
of the portion of the catheter body containing the openings against
the tissue to be ablated is achieved by conventional procedures
such as fluoroscopy, the use of markers, or other conventional
methods. Tissue contact is then verified by detecting an increase
of pressure inside the catheter. Energy is subsequently passed
through the electrode and ablation proceeds.
Thus, the invention also includes methods of operating an open
irrigated ablation catheter with an internal pressure sensor. The
operation of an ablation catheter, as previously described in
detail, consists of the following general steps. An ablation
catheter is first inserted into the patient. An operator maneuvers
the distal end (the end of the catheter with the electrode) by
manipulating proximal end control handle by any means well known in
the art including, but not limited to, pullwires. When the
electrode is in the proper location, the operator activates the
energy source (such as e.g., an RF generator) to allow ablation to
proceed. Proper location is verified by detecting an increase in
pressure inside the catheter.
The detection of the change in pressure inside the catheter is
based on measuring the pressure inside the catheter at any time
before tentative tissue contacting is made and then measuring the
pressure after tentative tissue contacting. Tissue contacting
arises only if the pressure after tentative tissue contacting is
greater than the pressure before tentative tissue contacting.
Thus, in one embodiment of the invention, the method of ablation
has the steps of (a) providing an open irrigated ablation catheter
with an electrode having a lumen and plurality of passages ways and
a pressure sensor inside the lumen of the electrode; (b) inserting
the catheter into a patient; (c) measuring the pressure in the
catheter inside the patient; (d) contacting a target tissue; (e)
determining if contacting of the target tissue has been made by (i)
measuring the pressure inside the catheter inside the patient after
tentative target tissue contact; and (ii) comparing this pressure
with that in step (c), with an increase in the pressure being
indicative of tissue contacting; and (f) ablating the target tissue
for a period of time and under conditions sufficient to ablate the
target tissue. The step of ablating the target tissue is achieved
by supplying energy, including RF, to the electrode. The step of
inserting may comprise the Seldinger technique as well as the other
techniques described. The step of inserting includes both the
inserting of the catheter and guiding the catheter to the target
tissue.
Pharmacological treatments may also be used in combination with
ablation procedures to relieve the atrial arrhythmia.
Although various embodiments of this invention have been described
above with a certain degree of particularity, those skilled in the
art could make numerous alterations to the disclosed embodiments
without departing from the spirit or scope of this invention. For
example, any means of measuring pressure could be used. All
directional references (e.g., upper, lower, upward, downward, left,
right, leftward, rightward, top, bottom, above below, vertical,
horizontal, clockwise, and counterclockwise) are only used for
identification purposes to aid the reader's understanding of the
present invention, and do not create limitations, particularly as
to the position, orientation, or use of the invention. Joinder
references (e.g., attached, coupled, connected, and the like) are
to be construed broadly and may include intermediate members
between a connection of elements and relative movement between
elements. As such, joinder references do not necessarily infer that
two elements are directly connected and in fixed relation to each
other. It is intended that all matter contained in the above
description or shown in the accompanying drawings shall be
interpreted as illustrative only and not limiting. Changes in
detail or structure may be made without departing from the spirit
of the invention as defined in the appended claims.
* * * * *